Electronic communication devices transfer information by transmitting and receiving electronic signals across distances. Prior to transmission, a signal must be converted or modulated into an electronic signal format that is suitable for the medium of the transmission, which may be wireless or be made via wire, optical cable or another medium. The format of the modulated signal must also be such that the signal will be understandable or capable of conversion by the equipment employed to receive the signal.
Though specific signal formats vary greatly, it is common for transmissions to be made in formats that are either analog or digital. Whether such transmissions are made in a digital or analog format will often depend on the purpose and type of equipment with which the signal is associated. For example, it may be appropriate to transmit a signal in an analog format for a sound-producing or voice device such as a radio or telephone. It may also be appropriate to transmit a signal in a digital format for a data device such as a computer network, digital telephone, or digital television signal transmission.
With the development of mobile communication devices such as cellular telephones and portable laptop computers that have wireless Internet capabilities, it has become increasingly important for individual components of such devices to be reduced in size for portability, especially as such devices become increasingly complex and equipped with an increasing number of components and capabilities. Required reductions in apparatus and component size, increases in component numbers, and other considerations can force limitations on the number of communication channels that are available. Where a limited number of communication channels are available, it may be necessary for multiple devices to share one or more of the channels.
Where multiple devices share one or more of the available channels, each channel must be itself capable of accommodating signals of the type used by each device sharing the channel. For example, where a communications platform includes a portable computer having a modem that operates with a cellular telephone to connect to a remote network connection, it may be necessary for a single shared channel to accommodate both the data (digital) signals of the portable computer and voice (analog) signals of the cellular telephone.
Ordinarily, a shared channel will accommodate only analog or digital signals at any single point in time. However, most devices can only recognize signals of a particular signal type. If one or more communication channels of a communications platform are shared, a signal received through a particular input signal line of the channel must therefore be directed to the interface of the appropriate device or devices of the platform. To properly direct an incoming signal to the appropriate interface, a communications platform must be able to both identify the type of signal that is being received and have the ability to direct the signal to an appropriate interface according to the type of signal that has been identified.